EP2947202A1 - Safety paper with watermark - Google Patents

Abstract

A dewatering screen (1) is described for the production of paper with at least one watermark, wherein the dewatering screen (1) comprises a wire mesh which is arranged outside the area of the watermark at a first height (6) and in the area of the watermark Means are arranged for generating the watermark. The screen is characterized in that the means are formed as discrete areas in the form of a plurality of lines and / or points representing a raster image of the watermark and the discrete areas as depressions (2) in the wire mesh relative to the first height (6) are. Further, a paper produced therewith is described and manufacturing method.

Description

TECHNICAL AREA

The present invention relates to a dewatering screen, to a method of manufacturing the same, and to a security feature for security papers made with such a dewatering screen which is e.g. intended for the production of security and value documents, and further such security documents. The watermark is designed as a multi-tone watermark, preferably in the form of a raster image.

STATE OF THE ART

Security papers, such as those used for banknotes, passports, identification documents, identity cards, birth certificates, securities, documents, government documents, etc., usually have e.g. Security elements in the form of watermarks that prove the authenticity of the paper. Such watermarks occur during the production of the security paper in the wet part of the paper machine by addition of the wet pulp (pulp) on a moving dewatering screen, which has different embossing depths.

Due to the embossing of the dewatering screen, the addition of paper fibers during sheet formation is influenced by the flow conditions in such a way that more paper mass accumulates in this area during deep stamping (depression in the wire relative to the middle wire height). Thus thicker and thereby darker appearing passages occur in the finished paper. On the other hand, in the case of embossing (increase in the sieve relative to the mean sieve height), less paper mass can accumulate there, resulting in thinner and, in the transparent, lighter areas in the paper. It can also create multitone watermarks with smooth gradual transitions between dark and light spots. The area of the paper surrounding the watermark with a substantially constant paper thickness (where the screen is at the middle screen height) is referred to as a velin area. The extension of sites thicker and darker than the vellum are natural limits. From a certain extent of the deep embossing accumulates again in the interior of the embossing similar mass of paper as on the Velinbereich. A spatially very extensive Embossing will therefore result in a watermark, which appears dark only in the edge area, but towards the center again assumes the gray tone of the surrounding velin area. In addition or as an alternative to embossing on the dewatering screen, elements (platelets, wires) can be applied to the dewatering screen, to which less paper mass can accumulate, similar to an embossing. Such elements also hinder drainage by the dewatering screen, resulting in an additional reduction of accumulated pulp. Such elements are usually soldered or welded metal wires or metal parts known as electrotypes. These technologies for the production of drainage screens are known in the art and, for example, in US Pat EP 0 458 973 B1 (there page 2: 8-11) described.

These electrotypes act on the one hand as a high embossing, on the other hand complete the Entwässungssieb in this area completely, whereby the addition of the paper mass is severely hampered and the finished paper particularly thin spots arise that appear very bright in transmitted light, which is why such watermarks as a highlight watermark be designated. One speaks in this context of single-level watermarks, as it can be achieved in contrast to the multi-level, obtained by embossing the Entwässerungssiebs watermarks, no grayscale transitions. However, in order to be able to obtain a kind of multi-tone effect with electrotypes, possibilities have been proposed in the prior art to execute these as platelets with a variable dot matrix.

From the patent EP-A-1 122 360 For example, a watermark based on embossing or electrotype is known, which is listed as a multitone watermark, which has transmitted in light and darker areas, which are arranged like a raster image, such that the lighter areas are more or less numerous and thus a large area of the subject. The brighter areas show lower optical density and consequently lower paper strength than the surrounding paper, and are differently distributed depending on the positioning in the watermark. By contrast, the darker areas in the raster image preferably correspond to the optical density and the paper strength of the surrounding paper. To produce such a rasterized watermark, among other things, a metal part, an electrotype serve, which has recesses in different sizes and is applied to the dewatering screen. This implementation becomes a multi-tone watermark imitated in the form of a grid and appears particularly bright in transmitted light. Such a feature is very concise and therefore easy to perceive.

An alternative manufacturing process is in WO-A-2011081561 proposed. In this case, a mask with micro-openings is applied to the dewatering screen. The diameter and distribution of the micro-openings on the mask are sometimes chosen so that accumulates paper mass in the micro-openings and thus creates a watermark with dark halftone dots in this area in the finished paper. On the other hand, the diameter and distribution of the micro-openings are defined in such a way that they serve for the pure dewatering of the paper pulp, ie without fibers attaching to the micro-openings. This should be a bright watermark with multi-tone effect in the form of a screening similar to the EP-A-1 122 360 However, due to the drainage properties of the micro-openings in partial areas of the mask, the low paper strengths in the lighter areas are reduced.

In EP-A-0 549 384 A bright watermark is described which is produced by a metal plate with drainage properties deposited on the dewatering screen. The drainage is carried out by regularly distributed elements in the metal plate, whose dimensions are so large that even paper mass can attach to these. As a result, a kind of screening in the form of equally distributed elements without multi-tone effect is generated in the watermark.

In DE-A-10 2005 042 344 On the other hand, to produce a watermark with a multi-tone effect, a metal plate with micro openings for dewatering the pulp is proposed, which is applied to the drainage sieve. The micro-openings are used for pure dewatering of the pulp, without accumulating paper pulp at the micro-openings. In order to still obtain a very bright watermark with multi-tone effect but without recognizable grid points, the metal plate is embossed with micro-openings together with the dewatering screen.

The disadvantage of such designed watermarks with bright areas is that depending on the reproduction of complex graphics, a large area of the paper has thin spots to achieve a low optical density and, consequently, there can be a significant weakening of the paper resulting in the formation of holes, tears, Breakages, etc. can lead.

A further disadvantage is that such bright watermarks in the form of a raster image with raster structure can be emulated more easily in contrast to true multitone watermarks, which, as described above, are formed by embossing the dewatering screen and contain both areas which are lighter than the surrounding velin area, such as areas which are darker than the surrounding velin area. Known techniques for the production of so-called spurious watermark are, for example, in DE-A-198 32 878 described. To imitate watermarks, a composition is allowed to penetrate or print on the surface of the paper so that the paper mass chemically changes there, and thus the transparency of the paper and thus brighter areas appear in the manner of a watermark.

In addition, the dewatering screens with watermarks described above are expensive to manufacture because they involve additional operations such as accurately positioning and applying metal or plastic parts to the dewatering screen. In addition, influences such as temperature, an acidic environment but also mechanical forces acting on the sieve can cause such metal parts to change or even come off. In this case, the paper machine must be stopped and the screen repaired or replaced, which is associated with maintenance costs and production losses.

PRESENTATION OF THE INVENTION

It is inter alia an object of the invention to provide a dewatering screen for producing a concise watermark, a method for producing such a dewatering screen, a method for producing a paper using such a dewatering screen as a tool, and security papers and papers provided therewith using such Entwässerungssiebs. The above-mentioned disadvantages of the prior art should be avoided. In particular, among other things, a security paper with a watermark should be specified, the watermark compared to conventional designs has increased visibility, security against counterfeiting and ideally also an increased recognition value. The essence of the invention consists in performing a watermark as a raster image of a plurality of introduced in the dewatering screen compared to the surrounding paper area dark appearing raster elements.

This object is solved by the subject matter of claim 1. The invention accordingly according to a first aspect relates to a dewatering screen for the production of Paper with at least one watermark, wherein the dewatering screen comprises a wire mesh which is arranged outside the area of the watermark at a first height (average screen height) and in which means for generating the watermark are arranged in the area of the watermark. The screen is characterized in that the means are formed as discrete areas in the form of a plurality of lines and / or points, which represent a raster image of the watermark. In addition, the discrete areas are provided as depressions in the wire mesh relative to the first height. Preferably, the discrete regions for forming the entire or at least a portion of the subject of the watermark are all formed with a same depth.

In a particular embodiment, however, the discrete regions may also have different depths, so that a kind of multi-tone effect can also be generated in the later paper by the different depths, such that continuous transitions are generated via a screening. For the purposes of this application, a depression is to be understood as meaning regions which, viewed from the side of the paper sheet to be formed of the screen, are in the form of depressions, i. in the form of concave or equally-recessed areas throughout, e.g. wherein the screen plane is offset away from the paper web in a confined area relative to the first height of the screen. For example, the pits may be in the form of grooves (formation of dark lines in the paper), e.g. circular depressions (formation of round dark spots in the paper), etc. may be formed. Such a depression in the lower region may particularly preferably have a widening of the stitches. If a recess forming the watermark at the end of the dewatering screen is indicated in the sequence with a depth in mm, this is the distance from the deepest depression of the watermark to an imaginary plane at the first level.

Under a depression in the context of this application but are also corresponding areas to understand in which the recess at least partially has no bottom, ie a recess is also a spatially limited through hole in the wire, in which the wires of the screen are severed in this area. Likewise a depression in the sense of this application are also corresponding areas in which the sieve meshes are not severed as compared to the surrounding area but considerably widened (without depression), so that a local permeability which results in a severance results.

In these depressions there is an increased deposition of pulp material respectively fillers, and / or an improved dewatering of the formed paper web, whereby paper areas are formed in the area of the depressions, which are then visible as dark areas.

The dewatering screen thus proposed accordingly permits the production of watermarks in which the pixels forming the screening (lines, dots) appear darker than the area surrounding the watermark, because more pulp material is deposited there. In contrast to the methods of the prior art, according to which raster watermark have always been proposed based on increases on the screen, and corresponding disadvantages had to be accepted paper strength, here are now the screening constituting picture elements to some extent as reinforced areas formed in paper and the disadvantages can be avoided. The above-described disadvantages of watermarks based on embossing, namely that no darkening results in the case of large subjects in areas far away from the edge regions of the subject, can thereby be comprehensively avoided by screening. This allows even large-scale watermarks to be displayed without the light-dark contrast being pronounced only in the edge region of the image and weakening in a region away from the edge. Accordingly, not only more stable watermarks can be provided by the proposed dewatering screen, and watermarks can be formed in much thinner paper layers than the prior art raster watermarking techniques, but it also results in improved contrast characteristics for larger representations ,

According to a first preferred embodiment, the dewatering screen is characterized in that the discrete areas are provided as wells with increased drainage, in which the mesh width of the wire mesh of the dewatering screen is widened relative to the surrounding area. This additional widening can be carried out selectively by subsequent manipulation after embossing, or else the embossing die itself can be configured such that a widening results.

The recesses are preferably offset from the first height at the lowest point by a depth in the range of 0.3 to 1.5 millimeters, preferably offset in the range of 0.5 to 0.8 millimeters.

If the depression is an effective aperture, then it is below the depth to understand the length of the formed there collar of mesh. Namely, as mentioned above, the depressions may also be provided as passage openings in the wire mesh of the dewatering screen, in which the wires of the wire mesh are interrupted in these areas.

The discrete areas that make up the raster image in its entirety may be formed as lines and / or as points.

If the raster elements are formed as lines, they preferably have at the respective widest point a width in the range of 0.5-5 millimeters, preferably in the range of 0.2-2.0 millimeters. The lines can also have a variable width along their length.

If the grid elements are formed as dots, they may preferably be in the form of circles, ovals, polygons, preferably in the form of squares, diamonds, triangles, rectangles, pentagons, hexagons. Instead of shapes, the dots may be represented as symbols, preferably in the form of letters, numbers, symbols such as e.g. Currency symbols etc. be formed. Preferably, in the largest dimension measured in the direction parallel to the screen plane, they have a length in the range of at least 0.2-5 millimeters, preferably in the range of 0.3-2 millimeters, and in the smallest dimension measured in the direction parallel to the screen plane a length in the range of 0.1-2 mm, preferably in the range of 0.2-1 mm.

The raster elements (lines / dots) can preferably have a variable size and / or shape as a function of the desired image and partly merge into each other in edge regions.

The dewatering screen is according to a further preferred embodiment characterized in that, with a wire diameter in the range of 0.1-0.3 mm, preferably in the range of 0.15-0.25 mm, in a first direction (chain, preferably in a round screen in the circumferential direction) per centimeter 20-40, preferably 25-35 wires, and in a second direction perpendicular to the first direction (weft, preferably axially extending in a circular screen) 15-35 wires, preferably 20-30 wires.

Preferably, the drainage screen is a round screen.

Behind (viewed from the paper side) the dewatering screen can be arranged according to a further preferred embodiment, a further support screen. This support screen is preferably connected at least pointwise with the dewatering screen (for example by spot welding).

The backing screen is normally somewhat coarser than the dewatering screen, i. larger mesh size and thicker wires than the dewatering wire, and preferably, with a wire diameter in the range of 0.1-0.3 mm, preferably in the range of 0.15-0.25 mm, in a first direction (chain) per centimeter 25-40, preferably 25-35 wires on, and in a second, perpendicular to the first direction (shot) 10-30 wires, preferably 15-25 wires.

Preferably / are Entwässerungssieb and Stützsieb, if both exist, both coined respectively. provided with the proposed wells according to the invention.

Furthermore, the present invention relates to a method for producing a dewatering screen as described above. The method is preferably characterized in that the discrete regions are produced by an embossing which preferably widens the mesh size, preferably by a stamp having the lines and / or points as elevations (for example produced by milling from a blank), and / or Discrete areas are created by drilling, punching, widening by needles, using laser, cutting torch, electric current.

Furthermore, the present invention relates to a method for producing a security paper with a watermark, wherein the motif forming the watermark of a plurality of raster elements, preferably in the form of lines and / or points is constructed, and in which these raster elements compared to the outside Watermark arranged portion of the paper have a higher density and thus a dark appearance in transmitted light. Preferably, such a method uses a dewatering screen as set forth above.

In this case, the dewatering screen can be immersed in the form of a round screen in the pulp to form the paper.

However, the dewatering screen may also be a wire, in which case the dewatering screen in the form of a wire with the pulp is subjected to the formation of the paper.

The paper is in both cases by dewatering on respectively on the screen and subsequent drying, optionally sizing and / or calendering and / or Coating, made.

Also possible is a subsequent application of a plastic layer on one side or both sides and possibly additionally a connection with a second paper layer, which may either also have such a watermark or not. Thus, a three-layer composite with two layers of paper and an intermediate layer of plastic or a central layer of paper and two outer layers of plastic, the proposed watermark is particularly suitable for such structures, since the watermark for thin paper layers (30-40 g / m ² , preferably 33-36 g / m ² , in particular 35 g / m ² ) is best suited and has a high contrast.

Furthermore, the present invention relates to a paper with a watermark, in which the subject forming the watermark is composed of a multiplicity of raster elements, preferably in the form of lines and / or dots, and in which these raster elements are arranged in comparison to the region located outside the watermark of the paper have a higher density and thus a dark appearance in transmitted light. Such a watermark is preferably made using a dewatering screen as set forth above, or preferably prepared in a process as set forth above.

Preferably, the watermark is thus constructed from a plurality of lines and / or points, which represent a raster image of the watermark, wherein these lines and / or dots are made darker in the transmitted light than the region of the paper surrounding the watermark. Typically, in the area of the subject of the watermark, the proportion of dark areas is in the range of 20-90 area%, preferably in the range of 30-80 area%, particularly preferably in the range of 40-60 area% (in each case based on the total area of the subject).

The paper is preferably a security or a banknote, wherein preferably the security or the banknote is made up of a plurality of such paper layers, preferably by at least one layer of a paper having such a watermark with another layer, which optionally also has such a watermark has, is connected via an intermediate plastic layer.

Further embodiments are given in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

ein Entwässerungssieb in einer Schnittdarstellung senkrecht zur Siebebene;

Fig. 2-5

Ausführungsformen von Wasserzeichen;

Fig. 6

ein digitales Rasterbild eines Wasserzeichens in a) und das Wasserzeichen auf einer Banknote in b); und

Fig. 7

eine Kombination mit einem Graustufen-Wasserzeichen.

Preferred embodiments of the invention will be described below with reference to the drawings, which are given by way of illustration only and are not to be interpreted as limiting. In the drawings show:

Fig. 1

a dewatering screen in a sectional view perpendicular to the screen plane;

Fig. 2-5

Embodiments of watermarks;

Fig. 6

a digital raster image of a watermark in a) and the watermark on a banknote in b); and

Fig. 7

a combination with a grayscale watermark.

DESCRIPTION OF PREFERRED EMBODIMENTS

According to the invention, a security paper for the production of security and value documents on a watermark with multi-tone effect, which is composed of a plurality of dark elements, which appear in transmitted light as a raster image.

For this purpose, as shown in the figures, the grayscale image to be generated is resolved in a first step into a black-and-white grid 20, and this grid 20 is embossed in the form of individual deeply embossed raster elements 14 (screen dots, grid lines) in the dewatering screen. In contrast to the embossing of a three-dimensional relief for generating a multi-level watermark, the embossing of the watermark 23 thus consists of a grid of numerous individual embossings instead of an embossment with continuous transitions. The technologies of embossing of conventional dewatering screens are known in the art and for example in the Wochenblatt für Papierfabrikation "Optimization options for the production of individual watermarked paper"; Issue 11/12, 2002 described. In the watermark 23, the darker elements are realized by deep embossing (depression in the sieve) 2 of the dewatering sieve 1 (cf. Fig. 1 ), this in such a way that locally more paper mass accumulates in these areas in papermaking and a higher paper thickness and, consequently, a higher optical density results in the finished paper at this point. In Fig. 1 the dewatering screen 1 is shown in a sectional view. The horizontal whole line indicates the mean height 6 of the dewatering screen in the area outside the watermark. The area outside the watermark is also indicated by the reference numeral 8. The area of the subject of the watermark is indicated by the reference numeral 7. At one point is illustrated how a depression can be configured as an opening 3.

The dewatering screen 1 is in Fig. 1 shown as a layer (thick black line), it comprises the wires (not shown) which form the screen, and typically have a diameter in the range of 0.2 mm. The wires are perpendicular braided over cross out, the chain is usually performed at a round screen in the circumferential direction and the shot parallel to the axis of the round screen. Also in Fig. 1 schematically shown with a dashed line is the surface of the paper formed, as well as the thickness of the paper. 4

The embossing depth of the dewatering screen, i. the distance between the plane 6 and the lowest point of the respective recess 2, is chosen so that there are no difficulties in the form of holes in the paper or paper tears during papermaking. The embossing depth is usually in the range 0.2-1.5 mm, preferably in the range of 0.3-1 mm, particularly preferably in the range of 0.7 mm. In order to produce such an embossing depth, a stamp is typically required which has a depth which is about 20-30% greater in the negative image. In the area of the embossed lines and / or points, the drainage can be increased, i. the stitches can be widened or even broken locally.

The stamping of the dewatering screen 1 can therefore also be carried out so that the wires of the dewatering screen break in the depth of the stamping due to the high deformation. This not only creates a stamping but also an opening 3 of the dewatering screen. Surprisingly, the breakage of the wires of the dewatering screen leads to no problems, but to a particularly dark expression of the corresponding grid point and thus to a further improvement of the contrast.

As an alternative to a raster image, executed by embossing, a watermark can thus also be realized by introduced in the form of a raster image openings of the dewatering screen. These can be implemented, for example, in the form of bores, punched holes, openings made by means of a laser, cutting torch, electric current or any other suitable technique. The openings may still have a downwardly oriented typically circumferential collar of mesh, but the openings can also be easily formed as holes in the mesh. In a further alternative embodiment, these openings can be achieved by widening the mesh size of the Entwässungssiebes done instead by a separation of the wires of the dewatering screen.

The darker elements 14 in the inventive watermark of the security paper have a higher optical density and thus a higher paper strength than the surrounding vellum paper 8. They can also have different levels of optical density, depending on how to choose the embossing depth of the dewatering screen 1.

By choosing different densities of the darker elements, a kind of multitone watermark with continuous transitions in the form of a rasterization can also be generated.

The locations between the darker elements have substantially the same optical density and thus the same paper strength as the surrounding vellum paper. However, in contrast to the darker spots, they are surprisingly brighter to the viewer than the surrounding vellum paper at the end. Preferably, these brighter areas all have the same optical density and thus the same paper strength as the surrounding vellum paper.

The dark and light elements may take on different size, distribution and shape and are not limited to a desired design to obtain a particular motif in the form of a raster image.

For example, in one embodiment, the dark and light elements may occur in the form of dots of different sizes, shapes and distribution. In a further embodiment, the dark and light elements may be the same size and / or regularly distributed. Preferably, the total area of the dark elements dominates the total area of the light elements 15 (cf. FIG. 2 ). Different appearing brightnesses of a certain range can thus be generated either by adjusting the size of the raster elements and / or by adjusting the density of the raster elements accordingly. The grid elements can touch or overlap.

In another embodiment, the dark and light elements may also appear as lines in different thicknesses and distribution. However, the lines can also be the same thickness and / or distributed, wherein preferably the dark elements 14 dominate (see. FIG. 3 ).

The shapes may be parallel in a single predetermined direction or in be arranged in different directions. Likewise, different forms of dark and light elements can be combined (cf. FIG. 4 ).

The size and distribution of the dark elements are chosen so as to produce a macroscopic effect in the finished paper, i. that with the naked eye the watermark is clearly perceived as a raster image.

In a particular embodiment, the size and distribution of the darker elements in the watermark can be chosen to give some sort of microscopic effect between the dark elements, which is of the order of magnitude of the screen structure, but different from and thus difficult to imitate. This effect occurs when the extent of the screen dot is on the order of the sieve mesh. This effect can be used as an additional authenticity feature, e.g. in a forensic analysis.

The dewatering screen 1 consists of interwoven metal or metal / plastic wires 5 and consequently leaves a screen structure in the finished paper during manufacture. The bright elements in the watermark 23 on the dewatering screen 1 correspond to the areas between the embossings. If one selects the areas between the deep embossings so that they essentially fall within the range of the mesh size of the sieve fabric of the dewatering sieve, then by combination of sieve fabric and deep embossing in the finished paper microscopically small, bright elements 15. Depending on the Siebmaschung these microscopic small, bright elements cause 15 fine lines, stars, crosses or the like (cf. FIG. 5 ).

In the raster image, halftone dots can be deliberately omitted, so that the deliberate omission of halftone dots causes recesses in the form of patterns, characters, numbers, etc. as bright spots within the halftone image (cf. FIG. 3 and 4 ; Globe). In a preferred embodiment, these bright recesses all have a substantially same optical density as the surrounding vellum 8.

In a further preferred embodiment, the recesses 24 in the raster image have an uninterrupted border 25 which has a substantially higher optical density than the surrounding vellum 8 (cf. FIG. 3 ; Word "grid"). As a result, the recesses 24 are highlighted in the raster image stronger. But the border 25 may also have its own arbitrary screening and be chosen so that a macroscopic and / or microscopic effect occurs in transmitted light.

By the above-mentioned embodiments, the recesses 24 in the form of Patterns, characters and encodings clearly highlighted. With this method, one also obtains an attractive effect in the manner of a highlight watermark without the associated disadvantages of the prior art, which requires a complex application by, for example, soldering, welding or sticking metal parts on the dewatering screen and a local weakening of the security paper ,

In a further embodiment, the halftone dots can condense, so that by the deliberate compression of the halftone dots forms 27, for example, as patterns, characters, numbers, etc. arise dark uninterrupted places within the halftone image (see. FIG. 2, 3 . 4 and 5 ; Symbol "Q")

Furthermore, halftone dots within the halftone image can be deliberately omitted in order to achieve a coding within the halftone image. Also halftone dots can be interconnected to also achieve a coding within the raster image. This is of particular interest because the watermark can be identified by suitable means, e.g. in the infrared transmitted light, registered with suitable camera systems and the hidden coding can be read. For example, the production lot can be coded in this way without substantially changing the appearance of the watermark according to the invention among the various production lots.

The security paper with the inventive watermark 23 can be made neutral white or in a shade. Surprisingly, with a nuanced, i. lightly colored paper has an increased contrast effect. The dark spots of the inventive watermark appear particularly dark, probably due to a relatively lower leaching of the coloring pigments and dyes and fillers in the low embossing of the dewatering screen 1.

The watermark 23 may represent a single motif or may be combined with other types of watermarks such as true multistage watermarks 30, shadow watermarks, electrotypes, spurious watermarks. In this case, the inventive watermark in combination may represent a separate motif or be integrated into a conventional watermark.

The inventive watermark integrated into a conventional watermark can also represent a separate motif or be part of the overall motif of the watermark.

The watermark 23 may also be used in combination with features such as mottled fibers,

Security threads, machine-readable features, fluorescent pigments, Upconverterpigmenten, etc. are combined. Further, it may be combined with other features applied or applied by finishing and / or printing such as screen printing, hologram foils, blind embossing, etc.

The security paper may in particular be a single- or multi-layered paper, preferably with a high percentage of cotton, but also coated paper or composite materials in which at least one layer is based on paper.

Such a paper composite of at least two paper layers and a plastic layer is, for example, in WO-A-2004076198 described. Of particular interest is the fact that in the case of the thin papers with watermarks described there with the watermarks according to the invention a particularly high contrast can be achieved between screening and the (especially thin) velin area.

Thus, in so-called multi-layered substrates, such as those resulting from the subsequent combination of several layers of different substrates and of which at least two layers paper-based each lie in a single layer a erfindungsmässiges watermark and / or combined with a conventional watermark or with another inventive watermark. The combination can be done in different layers, so that isolated motifs, but also combinations in transmitted light can be seen.

The security paper according to the invention can be produced on a long or round screening machine, the production preferably taking place on a round screening machine.

Example 1: Piana

In FIG. 6b an example of the inventive watermark is shown on a banknote. To obtain a 90 g / m ² watermark paper with the in Fig. 6b to produce illustrated inventive watermark is proceeded as follows. The starting point is a corresponding digital image template of the subject in the form of a grayscale image with a resolution of min. 300 pixels and 125 shades of gray. This image template is converted to a black-and-white "amplitude-modulated" halftone screen using the Adobe Photoshop® computer program (hereafter referred to as PS). In the coarsening filter, select a line grid with 25 lines / inch and a screen angle of -35 °. Subsequently, in the rastered halftone image, the value "70" in white Font color without contour inserted with a font size of 62. The finished raster image then corresponds to the representation in Fig. 6a ,

This raster image is now transferred as a negative image on a first blank blank in the size 100 x 100 mm by means of a CNC milling machine. The white areas are milled with a milling depth of 1 mm into the cavity blank so that the areas subsequently appearing in the watermark black respectively dark are provided as elevations. This results in the matrix form of the embossing stamp. Subsequently, a male mold is milled as a counterpart to the female mold from a second cavity blank in the size 100 x 100 mm by means of a CNC milling machine. Die and patrix form the finished die. Subsequently, with the finished die, a dewatering screen with a screen mesh of 32/24 (warp / weft threads, square centimeters, wire thickness: 0.17 / 0.18 mm) together with a support wire with a sieve mesh of 28/19 (warp / weft threads, square centimeter, wire gauge : 0.21 / 0.23 mm). The effective depth of the embossing in the dewatering screen was about 0.7 mm after this process. The dewatering screen then has numerous individual embossings in the area of the embossing. The embossed drainage and support screen is then mounted on a screen cylinder. The finished round cylinder is installed in a round screening machine for the production of banknote paper. For the production of a 90 g / m ² banknote paper with the inventive watermark in Fig. 6b A cotton mix of 75% cotton combing rings and 25% linters with a degree of burring of 45 ° SR (Schopper-Riegler) and a mean fiber length of 1mm is used. The filler used is titanium dioxide (anatase) in an amount such that the finished paper has an ash content of <5%.

In the finished paper, the watermark according to the invention consists of dark elements in the form of parallel lines. These dark elements correspond to the black parallel lines in the digital raster image (comparisons Fig. 6a and 6b ). Due to the deep embossing of the dewatering screen, these dark elements have a higher paper thickness (at least before calendering) and, consequently, a higher optical density than the surrounding vellum paper. The dark elements all have the same optical density. The bright elements in the inventive watermark in Fig. 6b correspond to the white areas in the digital raster image in Fig. 6a , The bright elements have the same paper thickness in the paper and, consequently, the same optical density as the surrounding vellum paper. The recess in the form of The value "70" also has the same optical density as the surrounding vellum paper. Due to the strong light-dark contrast of the screening but the bright elements, as well as the recess in the inventive watermark appear much lighter than in the surrounding vellum paper.

Example 2: Vreneli

In Fig. 7a the inventive watermark is shown in combination with a conventional grayscale watermark. In Fig. 7a is the inventive watermark the "cloak" of the woman. To obtain a 90 g / m ² watermark paper with the in Fig. 7a The combination of a watermark according to the invention and a grayscale watermark, which is shown, is carried out as follows. The starting point is an image template in the form of a grayscale image in which the overall motif is shown. The image template has a resolution of min. 300 pixels and 125 shades of gray. With PS, the "cloak" of the woman in the image template is marked and isolated from the overall motif. While the remainder of the overall motif remains as a grayscale image, the woman's isolated "cloak" is converted into a halftone grid of black grid rhythms and white background by amplitude modulation. As a setting for the screening, a diamond grid with 15 lines / inch and a screen angle of -45 ° is selected in PS in the coarsening filter. Subsequently, the value "10" in white font color and in font size 30 is inserted into the rastered halftone image. The value "10" also receives a black contour with a contour thickness of 12 Pt. The now finished raster image is merged with the rest of the original image to form an overall motif.

This overall motif is now transferred as a negative image to a blank blank in the size 100 x 100 mm by means of a milling machine. For the raster image, a milling depth of 1 mm is selected for the white areas. The non-screened portion of the overall motif, which will later form the conventional watermark, is milled as a three-dimensional relief with the maximum depth of cut of 1 mm in the cavity blank. Subsequently, with the finished die a dewatering screen with a screen mesh of 32/24 (as above) together with a support screen with a screen mesh of 28/19 (as above) coined. The effective depth of the embossing in the dewatering screen was about 0.7 mm after this process. The embossed dewatering screen thus has partial areas in the area of the embossing with continuous embossed transitions in the form of a three-dimensional relief (for the conventional Grayscale watermarks) and subareas with a grid of numerous individual embossings (for watermarks according to the invention). The depth of the deepest embossment of the three-dimensional relief for the conventional grayscale watermark corresponds to the depth of the embossings for the watermark according to the invention with a depth of approximately 0.7 mm. The embossed drainage and support screen is then mounted on a screen cylinder. The finished round cylinder is installed in a round screening machine for the production of banknote paper. For the production of 90 g / m ² paper watermark with the watermark in Fig. 7b A cotton blend of 75% cotton combing rings and 25% linters with a degree of buffing of 45 ° SR (Schopper-Riegler) and a medium fiber length (Kayaani) of 1mm is used. The filler used is titanium dioxide (anatase) in an amount such that the finished paper has an ash content of <5%.

In the finished paper, the watermark is a combination of inventive watermarks and conventional watermarks Fig. 7a shown. The inventive watermark consists of dark elements in the form of evenly distributed diamonds. Due to the deep embossing of the dewatering screen, these dark elements have a higher paper thickness (at least before calendering) and, consequently, a higher optical density than the surrounding vellum paper. The dark elements all have the same optical density. The bright elements have the same paper thickness in the paper and, consequently, the same optical density as the surrounding vellum paper. Due to the light-dark contrast of the screening, however, the bright elements in the watermark according to the invention appear distinctly lighter than the surrounding vellum paper.

The recess in the form of the value "10" in the watermark according to the invention has the same optical density as the surrounding vellum paper. The border (contour) of the value "10" on the other hand has the same paper thickness and thus the same optical density as the dark elements of the screening. The value "10" in the watermark according to the invention appears particularly bright in the manner of a highlight watermark in comparison to the surrounding vellum paper due to the strong light-dark contrast of the screening and the additional dark border.

In contrast to the watermark according to the invention, the conventional grayscale watermark shows no sharp light-dark contrasts, but soft gradual transitions between the gray levels. Although in the drainage sieve the depth of the deepest imprint for the conventional grayscale watermark is equal to the depth of the embossings for the watermark according to the invention and, consequently, the paper thickness in these areas should be the same in the paper, the optical density appears differently in these areas. Reason is the already mentioned strong light-dark contrast of the screening in the inventive watermark in contrast to the soft gradual transitions in the conventional grayscale watermark. By virtue of this light-dark contrast of the screening, the dark elements in the watermark according to the invention appear to have a higher optical density than the dark elements in the grayscale watermark having the same paper thickness.

Example 3: Vreneli

Instead of a 90 g / m ² banknote paper can be made with the embossed in Example 2 round screen and a 35 g / m ² watermark paper, which as a semi-finished product for producing a printing substrate according to WO2004076198 serves. For the production of a 35 g / m ² watermarked paper with the watermark in Fig. 7a A cotton blend of 90% cotton worsted and 10% linters with 63 ° SR (Schopper-Riegler) and a mean fiber length of 1.1mm is used. The filler used is titanium dioxide (anatase) in an amount such that the finished paper has an ash content of <10%.

The appearance of the entire watermark is as already described in Example 2 for the 90 g / m ² watermark paper. However, the watermark in the 35 g / m ² watermark paper is higher in contrast than in the 90 g / m ² watermark paper. The reason is the overall lower paper thickness in the area of the surrounding vellum paper. As a result, the light-dark contrast of the screening of the inventive watermark appears particularly strong, so that the bright areas and the recess in the inventive watermark, which have the same paper thickness as the surrounding vellum paper appear particularly bright.

Also the conventional grayscale watermark in Fig. 7a gains in contrast, but not as strong as the inventive watermark. Reason is the gradual smooth transitions of the grayscale in the conventional grayscale watermark.

Example 4: Apollo

In Fig. 7a the inventive watermark is shown in combination with a conventional grayscale watermark. In Fig. 7b the watermark according to the invention is a wing of the butterfly. To a 90 g / m ² banknote paper with the in Fig. 7b The combination of inventive watermarks and conventional gray-scale watermarks produced is performed as follows. The starting point is an image template in the form of a grayscale image in which the overall motif is shown. The image template has a resolution of min. 300 pixels and 125 shades of gray. PS marks a wing of the butterfly in the image template and isolates it from the overall motif. While the remainder of the overall motif remains as a grayscale image, the butterfly's isolated wing is converted into a halftone grid of black grid crosses by amplitude modulation. To set the rasterization, select a grid with 40 lines / inch and a grid angle of 0 ° in PS in the coarsening filter. In addition, a 0.65 x 0.65 mm symbol in the form of a cross with white fill and a contour of 12 Pt is inserted into the rastered halftone image. The finished raster image is merged with the rest of the original image to form an overall motif.

This overall motif is now transferred as a negative image to a blank blank in the size 100 x 100 mm by means of a milling machine. For the raster image, a milling depth of 1 mm is selected for the white areas. The non-screened portion of the overall motif, which will later form the conventional watermark, is milled as a three-dimensional relief with the maximum depth of cut of 1 mm in the cavity blank. Subsequently, with the finished die a dewatering screen with a screen mesh of 32/24 (as above) together with a support screen with a screen mesh of 28/19 (as above) coined. The effective depth of the embossing in the dewatering screen was about 0.7 mm after this process. The embossed dewatering screen thus has partial embossing areas with continuous embossed transitions in the form of a three-dimensional relief (for the conventional greyscale watermark) and subregions with a grid of numerous individual embossings (for watermarks according to the invention). The depth of the deepest embossment of the three-dimensional relief for the conventional grayscale watermark corresponds to the depth of the embossings for the watermark according to the invention with a depth of approximately 0.7 mm. The embossed dewatering screen is clamped together with a support screen on a screen cylinder. The finished round cylinder is installed in a round screening machine for the production of banknote paper. For the production of a 90 g / m ² banknote paper with the watermark in Fig. 7b is a cotton blend of 75% cotton Kämmlingen and 25% Linters with a grind 45 ° SR (Schopper-Riegler) and a mean fiber length of 1mm. The filler used is titanium dioxide (anatase) in such an amount that the finished paper has an ash content of <5%.

In the finished paper, the watermark of combination of inventive watermarks and conventional watermarks corresponds to the in Fig. 7b displayed watermarks. The dark elements are realized by the embossing of the Entwässungssiebes in the form of grid crosses, which accumulates more pulp than in the surrounding Velinbereich and consequently the paper in this area has a higher paper thickness (at least before calendering) and thus has a higher optical density. The areas between the low embossings in the dewatering screen (which form the bright elements in the watermark according to the invention in the later paper) are chosen such that they fall in the order of magnitude of the screen mesh. In contrast to Examples 1 to 3, in which one can recognize the screening with the naked eye in the inventive watermark, it comes in Example 4 by combination of mesh (which leaves its screen structure in the paper) and embossing to microscopic, bright elements in the finished Paper in the form of finely distributed dots.

In the inventive watermark areas with dark shapes in the form of large-scale points are also seen. These dark shapes in the watermark according to the invention imitate the pattern of the butterfly wing. The dark shapes are also realized by embossing the Entwässungssiebes, the depth of which is the same as that of the embossing of the grid crosses. However, the dark shapes in the watermark according to the invention appear darker overall than the surrounding grid. Reason is the already described microscopic effect of combination of mesh and embossing. Due to the finely distributed microscopically small bright elements, the screening generally appears "lighter", although the dark elements of the screening have the same optical density as the dark forms.

By contrast, the conventional grayscale watermark, in contrast to the watermark according to the invention, exhibits smooth gradual transitions between the gray levels.

LIST OF REFERENCE NUMBERS

1 dewatering Numbers) 2 deepening 22 Black shapes in digital black-and-white raster image (patterns, characters, codes, numbers) 3 Opening in the sieve 4 paper thickness 5 Wires of the sieve 6 Height of 1 outside the watermark 23 watermark 24 Bright recesses in the inventive watermark 7 Watermark area 8th Area outside the watermark; Velinbereich 25 Border of bright recesses in the inventive watermark 14 Dark elements in the watermark 15 Bright elements in the watermark 26 bill 18 Black halftone dots in the digital raster image 27 Dark shapes in the watermark according to the invention 19 White halftone dots in the digital raster image 30 Conventional multi-level watermark area 20 Digital black and white raster image 21 White shapes in the digital black-and-white raster image (patterns, characters, encodings,

Claims (15)

A dewatering screen (1) for the production of paper with at least one watermark, wherein the dewatering screen (1) comprises a wire mesh which is arranged outside the area of the watermark at a first height (6) and in which there are means in the area of the watermark of the watermark are arranged,
characterized in that
the means are formed as discrete areas in the form of a plurality of lines and / or points which represent a raster image of the watermark and the discrete areas are provided as recesses (2) in the wire mesh relative to the first height (6). Drainage screen (1) according to claim 1, characterized in that the discrete areas are provided as recesses (2) with increased drainage, in which the mesh width of the wire mesh of the dewatering screen (1) is widened and / or severed relative to the surrounding area (8) , Drainage screen (1) according to any one of the preceding claims, characterized in that the recesses (2) offset from the first height (6) at the lowest point by a depth in the range of 0.3 to 1.5 millimeters, preferably in the range of 0.5 to 0.8 millimeters are formed offset. Entwässerungssieb (1) according to any one of the preceding claims, characterized in that the recesses (2) are provided as through holes in the wire mesh of the Entwässerungssiebs (1), in which the wires of the wire mesh are interrupted in these areas. Drainage screen (1) according to any one of the preceding claims, characterized in that the discrete areas are formed as lines which have at the widest point a width in the range of 0.5-5 millimeters, preferably in the range of 0.2-2.0 millimeters, wherein the lines over the length of one can have variable width. Drainage screen (1) according to one of the preceding claims, characterized in that the discrete areas are formed as dots, preferably in the form of circles, ovals, polygons, or symbols, preferably in the form of squares, diamonds, triangles, rectangles, pentagons, hexagons, and in the largest dimension measured in the direction parallel to the plane of the sieve, have a length in the range of at least 0.2-5 millimeters, preferably in the range of 0.3-2 millimeters, and in the smallest dimension measured in the direction parallel to the sieve plane a length in the range of 0.1-2 millimeters, preferably in the range of 0.2-1 millimeters, wherein preferably the points have a variable depending on the desired image size and / or shape and can merge into each other in marginal areas partially. Drainage screen (1) according to one of the preceding claims, characterized in that , with a wire diameter in the range of 0.1-0.3 mm, preferably in the range of 0.15-0.25 mm, in a first direction (chain) per centimeter 20-40, preferably 25 Has -35 wires, and in a second, perpendicular to the first direction (shot) 15-35 wires, preferably 20-30 wires. Drainage screen (1) according to one of the preceding claims, characterized in that it is a round screen. Drainage screen (1) according to one of the preceding claims, characterized in that behind the dewatering screen (1) a further support screen is arranged, which is preferably at least pointwise connected to the dewatering screen (1), and wherein the support screen, with a wire diameter in the range of 0.1-0.3 mm, preferably in the range of 0.15-0.25 mm, in a first direction (chain) per centimeter 25-40, preferably 25-35 wires, and in a second direction perpendicular to the first direction (shot) 10-30 Wires, preferably 15-25 wires. Method for producing a dewatering screen (1) according to one of the preceding claims, characterized in that the discrete areas are produced by embossing, preferably widening the mesh, preferably by use of matrix-male die work, preferably by die-stamping Lines and / or points as elevations, and possibly corresponding male part, and / or that the discrete areas are produced by drilling, punching, needling, laser, cutting torch, electric current. A method for producing a security paper with a watermark, characterized in that a dewatering screen (1) according to any one of claims 1-9 is used, and this
immersed either in the form of a round screen in the pulp to form the paper,
or in that the dewatering screen (1) in the form of a wire is charged with the pulp to form the paper,
and the paper is produced in both cases by dewatering on the wire and subsequent drying, optionally calendering and / or sizing and / or coating. Paper having a watermark, preferably produced using a dewatering screen (1) according to one of the preceding claims 1-9, or preferably produced in a method according to claim 11, characterized in that the watermark is composed of a plurality of lines and / or dots which represent a raster image of the watermark, these lines and / or dots being darker in transmitted light compared to the area of the paper surrounding the watermark, and the areas arranged between these lines and / or dots having substantially the same density as the one Watermark surrounding area. Paper according to claim 12, characterized in that it is a security or a banknote, wherein preferably the security respectively the Banknote is composed of several such layers of paper, preferably by at least one layer of a paper with such a watermark with another layer, which optionally also has such a watermark, is connected via an intermediate plastic layer. Paper according to one of the preceding claims 11-12, characterized in that it comprises at least one paper layer with such a watermark, as well as a further paper layer, which preferably also has such a watermark or other security feature, wherein a plastic layer is disposed between the two paper layers , preferably in a basis weight in the range of 20-45 g / m ² , preferably in the range of 25-40 g / m ² , and further preferably the paper layers has a basis weight in the range of 20-45 g / m ² , preferably in the range of 25-40 g / m ² and between the paper layers, a security thread, preferably in registration with such a watermark, may be arranged. Paper according to one of the preceding claims 11-14, characterized in that it is at least partially based on cotton fibers, and / or that the paper is a security paper, preferably in the form of a banknote, a passport paper, or a check.

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